The present invention relates to integrated circuit (semiconductor) devices and methods of forming the same, and more particularly, to a nonvolatile integrated circuit devices and methods of forming the same
In general, semiconductor memory devices may be classified into volatile memory devices and nonvolatile memory devices. Volatile memory devices need a power to be supplied to retain data, while nonvolatile memory devices can retain data without power being supplied. A flash memory device is a type of highly-integrated nonvolatile memory device that is designed to have beneficial characteristics similar to those provide both by an erasable programmable read only memory (EPROM) and by an electrically erasable programmable read only memory (EEPROM).
Flash memory devices can be classified into a NOR-type flash memory device and a NAND-type flash memory device. The NAND-type flash memory device may be advantageous for providing high integration because a plurality of cells can be united into a single string and, thus, can be controlled in a united fashion. The NAND-type flash memory device generally includes ground select lines arranged on one side of wordlines and string select lines arranged on the other side of the wordlines. In general, spacers containing the same material are disposed between the wordlines and on the sidewalls of the string select lines and the ground select lines.
If the spacers are formed of a silicon nitride layer, a charge trap site is generally formed between the wordlines. As such, the interference between the wordlines may increase due to the high permittivity of the silicon nitride layer. If the spacers are formed of a silicon oxide layer, it may be difficult to scale down the intervals (reduce the spacing) of the ground select lines and the string select lines. The reason for this is that an electrical short may occur when a common source line and a bitline contact are formed between the ground select lines and between the string select lines.